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Message Posted: Thu, 25 Jun 2009 @ 10:30:26 GMT

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Subj:   Re: Blocking processes in Teradata
From:   DWellman

Hi Chaim,

I guess this really depends on what your DBA means by " overall performance of the entire Teradata database ".

In a Teradata environment, if there is a lock on a table from one query/process (e.g. an MLOAD job) and another query or process requires a conflicting lock then only this second query/process will be directly affected. That effect will vary, if it's a query and the "Locking NOWAIT" option is used then this second query will get an appropriate return code, but the main point here is that ONLY this second query/process is directly affected. By itself this situation won't cause the entire Teradata system to slow down.

Having said that, if this situation causes (for instance) a key query to be held and no other queries are allowed to run - due to scheduling constraints/requirements - then this will effectively slow down ALL of your Teradata processing. This isn't an issue with the Teradata database, just a side-effect of your particular requirements.

Also, if the table being locked is a key one to your processing or the Teradata system itself then again it will effectively mean that all processing is halted until the lock is resolved.

Does that help ?



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